Quick freezing process



Nov. 422, 1938. T WALTER 2,137,902

QUICK FREEZ ING PROCES S Filed NOV. 2l, 1936 4 2 Sheets-Sheeb 1 4,ffl IIIIII i ATTEST B lacmgw. Z2

ATTORNEY Nov. 22, 1938. Q T WALTER 2,137,902

QUICK FREEZING PROCESS Filed NOV. 2l, 1936 2 SheetsSheet 2 ATTORNEY 'Patented Nov. 22, 1938 UNITED STATES PATENTl @UNIE FREEZING PROCESS Application 'November El, i936, Ferial lilo. Multi it matroos.

This invention relates to a quick freezing process for foods and to apparatus for carrying out the process.

One of the objects of the invention is to provide an improved quick freezing process.

Another object of the invention is to provide apparatus for carrying out an improved quick freezing process.

Other objects will be apparent from the description and claims which follow.

As is well known, quick freezing involves ad vantages over slow freezing in that in quick freezing the ice crystals formed in the foods are small and do not rupture the cell walls, avoiding an excessive moisture loss by cellular leakage upon defrosting.

The present invention is particularly adapted for quick freezing poultry.

Embodiments of apparatus involved in the' present invention are shown in the drawings.

Figure 1 is a schematic view, partly in section,

of one form of apparatus involved in the present I invention.

Figure 2 is a side view, partly in section, of another form of apparatus Vwhich may be employed in carrying out the process of the present invention.

' Referring now more particularly to Figure 1:

Retort I is provided with a removable head 2 at one end. Head 2 may be held tightly in position by any suitable means as bolts 3 and wing nuts 4, and is removed to charge the retort with product to be frozen. Product 5 is placed in retort I on rack 6. It will be noted that retort I is provided with vapor chamber 1 to avoid return of slugs of liquid through pipe 8 to compressor 9.

The present invention is carried out with a suitable liquid refrigerant, as for example liquid carbon dioxide. Before the system is started, air Ais removed through pipe I0 provided with valve II. Pipe 8 is provided with valve I2 and returns gaseous refrigerant to compressor 9 from chamber 'l of retort I. Compressor 9 delivers the compressed refrigerant in gaseous form through line I3 to condenser I4 which may be of any suitable type and is designed to discharge the liquefied refrigerant through pipe I5 into receiver I6. Re-

' ceiver I6 is preferably of large capacity and should contain enough of the liquefied refrigerant to fill retort I to the desired level.

Liquid refrigerant is delivered from the receiver I6 to retort I through pipe I1 provided with Valve i2 is employed for closing the retort ofi from the compressor. Pump iii is provided to re turn to the receiver any liquid refrigerant re maining in retort i after completion of 'the freezing operation prior to opening the retort for it removal of the product. Liquid refrigerant in the retort returns to receiver it through line 2t provided with valve 2| and line il? provided with valve 23. Gauge 24 is provided for visual observation of the level of liquid refrigerant in li) retort i.

The apparatus shown in Figure l may be operated in the following manner:

Assuming valves I2 and I8 are closed and that receiver I6 is filled with liquid refrigerant under l5 suitable pressure and temperature conditions, retort I is open at head 2, the desired quantity of product is loaded into the retort and cover 2 tightly closed. Valve II is opened slightly to allow air retained in the retort to escape. Valve I8 20 is next opened and a suitable quantity of refrigerant permitted to flow into retort I through pipe I1. A sufiicient quantity of refrigerant is admitted to retort I to completely cover all product to be refrigerated, the level being observed in gauge 25 24. When it appears that substantially all air within the retort I has b'een discharged through valve I I, this valve is closed. Pressure is now built up in retort I. The pressure will depend upon the nature of the refrigerant and the temperature of the product and retort. Valve I8 is closed after a suitable quantity of refrigerant has been admitted to the retort. Compressor 9 is then started and valve I2 opened, starting the 'pumping down process. As soon as compressor 9 starts to re- 35 move gas from retort I, some of the liquid refrigerant in retort I evaporates, reducing the temperature of the mass of liquid refrigerant and the surrounding materials. As the vapor pressure in retort I is lowered, the temperature 40 of the refrigerant is lowered. With such refrigerants as liquid carbon dioxide, very low temperatures may be obtained, and consequent rapid chilling of the product in trays 6.

'I'he shell of the retort is heavily insulated 45 against the transfer of atmospheric heat into the system as by insulation 25. Similarly the receiver is heavily insulated as by insulation 26.

As the freezing of the product proceeds, if more refrigerant is desired to maintain complete sub- 50 mersion of the product, the desired quantity may be admitted at will through valve I8.

After freezing has proceeded to the desired extent, valves 2I and 23 may be opened and pump I9 placed in operation to pump the remaining 55 liquid refrigerant from retort I into receiver I6. After all of the refrigerant in retort I has thus been returned to receiver I6,` valves 2l and 28 may be closed. Compressor 9 should continue to operate until the'pressure in retort i has been reduced to atmospheric pressure or less. Compressor 9 may then be stopped and the retort I 'opened with safety to permit removal of the product.

Any liquid refrigerant which may remain inv or about the product will be rapidly and completely evaporated from the product during subsequent handling.

In the refrigeration of foods, it is essential that the refrigerant be one which is not absorbed and must be one which is relatively inexpensive, nontoxic, convenient to handle, and which has physical and thermal characteristics making possible extremely low temperatures and rapid rates lofl heat exchange. Liquid carbon dioxide is such a refrigerant.

Referring now more particularly to Figure 2:

Retort I is provided with head 2 which may be securely fastened to retort I by means of bolts 3 and wing nuts 4. Product 5 may be placed upon racks 2l. It is understood, of course, that retort i must be sufficiently strong to 'withstand the ordinary working pressures to be imposed upon it. Retort I is covered with insulation 25 and receiver I5 is covered with insulation 26. Receiver i6 functions as a liquid receiver and as an evaporator and is connected to retort I by pipe Il provided with valve i8. Chamber I 6 is adapted to hold a quantity of liquid refrigerant to any suitable level, the space 2t above the liquefied refrigerant being occupied by the refrigerant in its gaseous state.

A suitable compressor machine 9 is included in the`systern to deliver the hot compressed gas to the condenser ld through pipe i3 where it is liqueed and returned to receiver iii through pipe iii. Airfpump 2@ is provided to exhaust chamber i of air at the start of the freezing cycle communicating with retort i through pipe Sti' and pipe i0 provided with valve 3i. Pipe 3i! is provided with valve 32. Air withdrawn by pump 29 is exhausted through pipe 33. The pump 34, suitable for handling liquid refrigerant, is employed to return quantities of liquid refrigerant from retort l to receiver l at the end of the freezing process. Pump 34 removes refrigerant from retort i through pipe 35 provided with valve 3d, and returns the refrigerant from receiver i5 through pipe 3l communicating with pipe i5. Retort i is provided with safety valve 38 to prevent damage to the apparatus in, the event of excessive pressure.

Duringthe operation of the system, gas evaporating from the liquid refrigerant in retort i is Withdrawn through pipe 39 communicating with pipe dil at d i. Gaseous refrigerant formed in the receiver I5 may also be withdrawn through pipe dil to compressor 9. Pipe il@ is provided with valve d2 between compressor it and T di.

The operation ofthe apparatus will be readily understood by reference to Figure 2. Assuming that the receiver I '6 is nearly full of liquid refrigerant such as liquid carbon dioxide, the liquid being at room temperature, valves i'and 32 are closed. Valve d2 is opened` and the compressor 9 started. The vapor pressure in space 2S will be reduced and some ef the liquid refrigerant will be evaporated. This evaporation will bring about a reduction in the temperature of the remaining refrigerant. .As the compressor continues to operate, the temperature of the liquid refrigerant continues to lower, concurrently lowering the pressure within space 28. The com.` pressed gas passed into the condenser I4 is liquefled and returned to receiver I6. After'a period of time, any desired temperature for the liquid refrigerant may be obtained within the limits of the physical characteristics of the refrigerant. For example, if the liquid refrigerant is carbon dioxide and it is desired to operate ata temperature of 0 F., a. pressure of approximately 300 pounds per square inch will be maintained in receiver I6. After the desired temperature oi the refrigerant has been reached, it will be maintained while the compressor is operated at the suction pressure corresponding to that temperature.

Retort l is now filled with a quantity of the product to be refrigerated, head 2 tightened in place, and air pump 29 started for the purpose of extracting air from chamber I and to avoid the introduction of substantial quantities of unliqueflable gases into the system. If desired, a simple blow-off valve may be provided as a substitute for air pump 29 permitting the valves to remain open after a small quantity of liquid carbon dioxide is introduced into chamber I. The evaporating carbon dioxide will tend to dispel the air through the blow-off valve, but this method would entail a loss of refrigerant and, consequently, the pump is preferred.

After the chamber i has been well exhausted by the action of air pump 29, valves I8 and 32 are opened, permitting the prechilled liquid refrigerant to enter the retort and completely or partially flood the interior of retort i. Liquid refrigerant comes in contact with the product to be chilled at the minimum temperature of the refrigerant, causing freezing of the product to commence immediately. Contact of the liquid refrigerant with the warm. product results in a heat exchange and the evaporation of some of the liquid refrigerant. The gases thus formed are drawn oi through pipe line 3S to the compressor 9, maintaining a minimum temperature of the refrigerant at a constant value.

The system assures that the maximum pressure in retort i is that pressure corresponding to the minimum temperature of the refrigerant. The carbon dioxide operating from 0 to 50 F. the maximum pressure in the chamber will be about 300 pounds. which may exist in receiver i6 will be much higher than this and will correspond to the vapor pressure of the liquid refrigerant at the highest temperature that may prevail in the receiver, which may be as high as 100 or more F.

After the system has operated sufficiently to chill or freeze the product to the desired degree, the freezing operation is stopped by closing valves i8 and 32, and starting pump 34, drawing oil from the bottom of the retorti the liquid refrigerant remaining therein and returning it through pipe 3l to receiver I6. The refrigerant is not heated before being returned to receiver i6, but is returned at approximately its minimum temperature. After all of the liquid has been withdrawn from retort I, pump 34 may be stepped and valve 36 closed. Valve 42 may be closed and valve 32 opened. With the compressor operating, retort I may be pumped down to atmospheric pressure. It is now in condition for opening and removal of the product.

The apparatus which has been described re- On the other hand, the pressure suits in extremely rapid freezing, permitting a chicken to be frozen solid in about 15 minutes. This rapid freezing is brought about by the extremely low temperature involved and the intivmate contact between the freezing medium and the product to be frozen. Due to the efficiency of the apparatus, its capacity is high and the investment relatively low.

I claim:

1. In a freezing device, a product retort, a pipe from said retort communicating with a compressor, a condenser connected with said compressor, a liquefied refrigerant receiver connected' with said condenser, a pipe communicating with said receiver and said retort, and a pump for returning liquefied refrigerant from said retort to said receiver as desired.

2. In a freezing device, a product retort, a pipe from said retort communicating with a compressor, a condenser connected with said compressor, a liquefied refrigerant receiver connected with said condenser, a pipe communicating with said receiver and said retort, a pump for returning liquefied refrigerant from said retort to said receiver as desired, and an air vent provided with a valve for preventing excessive pressures within the retort.

3. In a freezing device, a product retort, a pipe from said retort communicating .with a compressor, a condenser connected with said compressor, a liquefied refrigerant receiver connected with said condenser, a pipe communicating with said receiver and said retort, a pump for returning liquefied refrigerant from said retort to said receiver as desired, an air vent provided with a valve for preventing excessive pressures within the retort, a valve positioned between said receiver and said retort, a pipe connecting said pump and said retort, a valve in said last mentioned pipe, and a pipe connecting said pump and said receiver.

4. In a freezing device, a product retort, a pipe from said retort communicating with a compressor, a condenser connected with said compressor, a liquefied refrigerant receiver connected with said condenser, a pipe communicating with said receiver and said retort, a pump for returning liquefied refrigerant from said retort to said receiver as desired, an air vent provided with a valve for preventing excessive pressures within the retort, a valve positioned between said receiver and said retort, a pipe connecting said pump and said retort, a' valve in said last mentioned pipe. a pipe connecting said pump and said receiver, and

means including an air pump having means communicating with said retort for exhausting air from said retort.

5. In apparatus for quick freezing food in a liquefied refrigerant, a freezing retort, a liquefied refrigerant receiver connected with said retort by a pipe, a valve in said pipe, a pipe leading from said receiver to a compressor, said last-mentioned pipe provided with a valve, a pipe leading from said retort to said compressor. said last mentioned pipe'provided with a valve, a pipe leading from said compressor to a condenser, a pipe leading from said condenser to said receiver,apipe leading from said retort to an exhausting air pump, a pipe leading from said retort to a liquidl l5 pump, a valve in said pipe between said retort and said liquid pump, and a pipe leading from said liquid pump to said receiver.

6. In a quick freezing device, a closed retort having openable means for admitting product thereto, a liquefied refrigerant receiver communicating with the retort, means controlling the ow of liquefied refrigerant from the receiver to the retort, a compressor condenser circuit connecting the retort with the receiver, said compresser condenser circuit being adapted for withdrawing gaseous refrigerant from the retort and for delivering liquefied refrigerant to the receiver, and means for delivering liquefied refrigerantI from the retort to the receiver.

7. In a quick freezing device, a closed retort having openable means for admitting product thereto, a liquefied refrigerant receiver communicating withthe retort,meanscontrolling the flow of liquefied refrigerant from the receiver to the retort, a compressor condenser circuit connecting the retort with the receiver, said compressor condenser circuit being adapted for withdrawing gaseous refrigerant from the retort and for delivering liqueed refrigerant to the receiver, and means including a liquid pump for delivering liquefied refrigerant from the retort to the receiver.

8. The method of quick freezing food products which comprises submerging the food in a liquefied refrigerant in a closed system under pressure, continuously withdrawing gaseous refrigerant, continuously returning liquefied refrigerant at a substantially constant low temperature until completion lof the freezing process and thereafter withdrawing all of the liquefied refrigerant from the system.

. CHARLES T. WALTER. 

